How can you tell if a German Shepherd is purebred? Is is true that if a dog does not have those two black dots on either side of his face then he is not a purebred German Shepherd? Also are there any German Shepherds that are completely black and have tan paws?Also, what is it mean if a German Shepherd is an East German Shepherd?Also, is it true that if you feed your dog a high protein diet it will prevent the dog from getting hip dysplasia?

Some German Shepherds with a hint of something else in them can look identical to purebred German Shepherds so I would imagine the answer to that is with great difficulty. Maybe a breeder can enlighten you.
The black dots on the side of the face will not be visible on a dog with a black face or a white dog so that's not true. Some sable dogs don't have them too.
Yes you can get black dogs with tan paws.
East German Shepherd ............. no idea! Never heard of it.
A high protein diet will not prevent HD but unless your dog is extremely active I wouldn't feed it.
Lara x